In the strictest sense, there is no known example of an organic magnetic monomolecular film or organic magnetic built-up film. Examples of organic magnetic material have been barely realized so far, and nothing is reported about organic magnetic crystals.
Although not yet advanced to the stage of expression as magnetism, studies on Langmuir-Blodgett (LB) film by measurement of electron-spin resonance (ESR) have been attempted. As film components, copper stearate (J. Messier and G. Marc, J. Phys., Paris, 32, 799, 1971), and copper dithiocarbamate with a fatty acid of 18 carbon atoms (P. A. Chollot, J. Phys., C: Solid State Phys., 7, 4127, 1974) are used. In the category of thin films, as disclosed in Japanese Laid-open Patent Hei. 3-160708, an example is known of an organic magnetic thin film formed by plasma polymerization.
In attempting to endow a high molecular weight compound with magnetic properties, a method is known whereby the spin direction is aligned by attaching a functional group having radicals to the pendant portion extending from the main chain.
To obtain organic magnetic materials, therefore, it is believed necessary to satisfy the following two conditions:
First, heightening the spin density by placing multiple unpaired electrons stably in an organic material, and second, increasing the spin rate of parallel arrangement.
However, in the known organic magnetic materials in which the properties of the organic molecule itself are reflected, both spin density and rate of magnetization are still low. This is probably because improvement of spin density and control of spin arrangement are not sufficient. In this circumstance, at present, materials possessing practically sufficient magnetism have not yet been reported.
Strictly speaking, organic molecules having unpaired electrons possess magnetism individually. In most cases, however, when the molecules are gathered and crystallized, they cancel each other, and magnetism is largely lost throughout the crystal. Therefore, in order that the crystals or molecule sets may possess magnetism on the whole--that is, expressing magnetism macroscopically--the molecules must be arranged solidly in order to align their spin direction. Hitherto, in most cases of organic magnetic materials, in the method of aligning spin direction, it has been attempted to capture into the forming matrix other stable substances similar to inert gases or magnetic molecules in a solid structure. The magnetism is then confirmed by measurement.